Method for making a finished part comprising a zone for providing a passage

ABSTRACT

The invention relates in particular to a facia panel designed to make it possible for an airbag to pass through it at the time the airbag is inflated. In accordance with the invention, the part includes a plastic support element ( 8 ) having a reduced thickness in comparison to its other dimensions; a connecting sheet ( 6 ) joined to the support element; the part presenting a special zone ( 15 ) which forms a door and is designed to make it possible to create a passageway, the zone being delimited by a periphery constituted by an embrittled portion ( 14 ) presenting two extremities of an articulating portion which defines, between the two extremities, an articulation axis overlapped by the sheet; along at least the major part of the embrittled portion, the sheet is present on either side of the embrittled portion; and the sheet is present over the greater part of the special zone.

BACKGROUND OF INVENTION

1. Field of Invention

The invention relates to a method for producing a finished partcomprising a zone which forms a door for an airbag and is designed toallow a passageway for the airbag to be created, as well as to such apart and to an assembly comprising the part.

2. Description of the Prior Art

More particularly the invention has applications in the field ofautomotive interior design, where it is especially relevant to theproduction of facia panels and door panels.

The object of the invention is to find a straightforward, reliable andinexpensive way of producing durable and reliable parts that enable apassageway to be created in a satisfactory manner.

In order to produce such a part, U.S. Pat. No. 5,395,668 and FR-B-2 725950 disclose a method featuring the following steps:

a) producing a part comprising a support element made from plasticsmaterial(s) which is of reduced thickness compared to its otherdimensions, and a connecting sheet which extends substantially along thesurface of said support element,

b) incorporating in the part the special zone which forms a doordelimited by a periphery constituted by an embrittled portion which hasbeen mechanically weakened between two extremities and by anarticulating portion which defines, between said two extremities, anarticulation axis overlapped by the sheet.

However, this method is not entirely satisfactory. In particular, as faras the airbag is concerned, opening the door gives rise to fractures andeven cracks, which tend to propagate within the part. Since thesefractures or cracks are not restricted to the articulating portion,there is a danger of fragments of said part breaking away and beingprojected at the occupants of the vehicle and injuring them.Furthermore, there is a dispersion of the force deployed by the airbag,requiring the airbag to exert very great pressures to succeed in openingup the door.

Although it would have been possible to employ quality materials thatare able to withstand stresses without fracturing, this solution isnevertheless comparatively expensive.

SUMMARY OF THE INVENTION

In order to resolve this problem the invention proposes that:

the connecting sheet employed presents a greater length and breadth thanthose of the special zone, and

during stage b), the embrittled portion is produced in such a mannerthat the connecting sheet is present to either side of the embrittledportion along at least the major part of said portion, and that theconnecting sheet is present over at least the greater part of thespecial zone.

Accordingly, the retaining sheet is arranged in that section of the partwhich shows the greatest tendency to fracture on account of themechanical stresses, and catches any fragments.

The function of the connecting sheet in the present invention istherefore different from those in U.S. Pat. No. 5,395,668 and FR-B-2 725950, where it acts as a reinforced articulation means. That is also whyin those documents it is disposed near to the articulating portion.

Accordingly, if appropriate it would be possible to provide for aconnecting sheet to be present over the major part of the door in orderto catch the fragments, and to have a connecting sheet present in thevicinity of the articulating portion in order to reinforce the joint ifthe mechanical stresses involved called for this.

The length and breadth of the sheet represent its external dimensionsperpendicularly and along the articulation axis, respectively.

According to one preferred application of the invention, during stageb), in at least part of the embrittled portion a cutout issimultaneously made in the sheet and the support is mechanicallyweakened by excising a part of its thickness.

This straightforward solution makes it possible on the one hand toquickly obtain a particularly efficient reinforcement of the support asfar as the edge of the embrittled portion, and on the other hand tosatisfactorily weaken said support mechanically, by precise positioning,relative to one another, of the cutout in the sheet and the mechanicalweakening of the support. The cutout is preferably continuous and runsthrough the full thickness of the sheet, although this is not necessary.

In order to resolve the foregoing problems still more effectively andsimply, the invention proposes:

during stage a), carrying out the following operations:

introducing the connecting sheet into a mould cavity, and

introducing the plastics material into the mould cavity, said plasticsmaterial making contact with the sheet,

during stage b), producing the embrittled portion in such a manner thatit is wholly and strictly enclosed within the sheet.

Accordingly, the connecting sheet surrounds the perimeter (the entireperiphery) of the door and covers the whole of the door. On either sideof the embrittled portion the support is reinforced by the sheet overthe whole of said portion. The moulding process makes it possible toproduce the part in a straightforward and satisfactory manner,especially by making it possible to place the sheet in position easily,with the result that said sheet is present everywhere that it is desiredto produce the cutout.

In order to obtain even better quality parts in a straightforward andreliable manner, the invention proposes:

the use of a mould comprising a mould cavity, a female die, a male dieand an insert adapted to be moved between a retracted position and anadvanced position, said movable insert being inserted into a cavity inthe male die, thereby producing a slot between it and the male die whenthe insert is in the retracted position and moving further away from themale die when it is displaced towards the advanced position,

during stage a), introducing the sheet into the mould cavity, with themovable insert advanced; then by retracting the movable insert a foldedportion of the sheet is set in said slot; the plastics material is nowintroduced into the mould cavity.

In this manner a part is obtained wherein the sheet is in the form of aloop facing the articulating portion. The pivoting of the door about thearticulation axis is thus facilitated by the excess length of the sheetformed by this loop. Moreover, the production of the support, itsconnection to the sheet and the accomplishment of this loop are allbrought about in a single operation.

According to a further practical feature, the invention proposes:

during stage a), producing the part in such a way that the sheet ispresent over all or at least the majority of the part, perpendicularlyto the articulation axis,

attaching the part by fixing it to a body, and

joining the sheet to the body.

The presence of the sheet over all or at least the majority of the partperpendicularly to the articulation axis considerably reduces the riskof fragments of the part being thrown off. The joint between the sheetand the body ensures that the part will continue to be retained inrelation to the body, in so far as there is no danger that theinflexible sheet will fracture.

In order to facilitate the fixing, i.e. connection, of the sheet to thebody, the invention proposes:

during stage a), sticking out a tongue of said sheet from the mouldcavity,

and joining said tongue of the sheet to the body.

A further object of the invention is a composite finished part. U.S.Pat. No. 5,395,668 and FR-B-2 725 950 describe a part comprising:

a support element made of plastic and having a reduced thicknesscompared to its other dimensions,

a connecting sheet joined to the support element, said part featuring aspecial zone which forms a door for an airbag and is designed to allowthe creation of a passageway, said zone being delimited by a peripheryconstituted by an embrittled portion having two extremities and anarticulating portion which, between said two extremities, defines anarticulation axis overlapped by the sheet.

However, this part presents the drawbacks outlined above. In order toovercome these drawbacks the invention proposes:

that along at least the major part of the embrittled portion the sheetshould be present on either side of said portion, and

that the sheet should cover the majority of the special zone.

According to another advantageous feature, the invention proposes thatthe sheet should extend, perpendicularly to the articulation axis,beyond the articulating portion and at least as far as the edge of thepart.

This reduces the risk that the pressure exerted by the airbag on thedoor and the resulting inertia on said door will cause the fracture orat least the start of a fracture of the part in a directionperpendicular to the articulation axis.

The invention furthermore relates to an assembly incorporating the part.According to the invention this assembly is characterised by the factthat:

it additionally comprises a body onto which the part is fixed, and

the sheet is joined to the body.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become still clearer from the following description,referring to the accompanying drawings in which:

FIG. 1 illustrates a first stage of a method in accordance with theinvention,

FIG. 2 illustrates a second stage of the method in accordance with theinvention,

FIG. 3 illustrates, in situ, a finished part produced after the stagesshown in FIGS. 1 and 2,

FIG. 4 is a view in the arrowed direction IV from FIG. 3,

FIG. 5 illustrates, in situ, the finished part from FIG. 3, followingthe inflation of an airbag,

FIG. 6 is a scaled-up view illustrating a variant of the finished partfrom FIG. 3,

FIG. 7 illustrates another variant of the finished part, in a sectionalview in the arrowed direction VII—VII from FIG. 3,

FIG. 8 illustrates yet another variant of the finished part, in asectional view in the arrowed direction VII—VII from FIG. 3,

FIG. 9 illustrates a variant of the connecting sheet,

FIG. 10 is a cross-section showing a finished part incorporating anothervariant of the connecting sheet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 depict a mould 12 comprising a fixed part 12 a constitutedhere by a concave female die and a movable part having a convex male die12 b and a movable insert 12 c. These two parts are movable with respectto one another between a closed position and an open position. Theopening/closure of this mould is controlled in translation in a mouldopening/closure direction by an actuator (not shown). Between them thefixed part and the movable part define a mould cavity 10.

The movable insert 12 c is connected to the male die 12 b by an actuator3 which controls its displacement with respect to the male die 12 b bytranslation substantially following the mould opening/closure directionbetween an advanced position and a retracted position, as illustrated bythe arrow 5.

In the retracted position, the movable insert 12 c is inserted into acavity 7 on the male die, leaving a slot 4 between one 11 of its sidesand an adjacent side 9 of the cavity 7 of the male die.

In FIG. 1, the mould 12 is shown in the open position the fixed part 12a and the movable part 12 b, 12 c are quite remote from one another. Aconnecting sheet 6 i s disposed resting against the male die 12 b andthe movable insert 12 c, and said sheet is affixed to these. Inparticular, part of said sheet rests against the side 11 of the movableinsert 12 c.

The retaining (affixing) means (not shown) of the connecting sheet 6 areconsidered as known and they may notably include pins or adhesive.

The movable insert 12 c is now retracted until it rests against thefloor of the cavity 7 on the male die. As depicted in FIG. 2, duringthis operation the edges 11 and 9 respectively of the movable insert andof the male die draw closer to one another, trapping between them, inthe slot 4, a non-terminal folded part 2 of the sheet. This folded partdefines a loop 2 or meander. The thickness e of the slot issubstantially equivalent to twice the thickness of the sheet 6.

Next the mould 12 is closed, the fixed part 12 a making contact with themovable part 12 b, 12 c. The mould cavity is then filled bypressure-injecting plastics material into it from the fixed part 12 a ofthe mould. The plastics material makes contact with the connecting sheet6 and adheres to it. Since the width and thickness of the slot 4 aresubstantially the same as that of the loop and since, moreover, saidthickness is very small, the viscosity of the plastics material does notallow it to penetrate said slot 4.

In FIGS. 3 and 4, the part 1, obtained after cooling the plasticsmaterial and removal from the mould, defines a facia panel featuring anon-visible concave face 1 b and a visible convex face la when the faciapanel is in situ. These two faces are separated by the thickness of thepart 1.

On the non-visible side, the connecting sheet 6 extends over the surfaceof the facia panel and more particularly over the surface of a supportelement 8 into which it is integrated. This support element 8 isproduced from the plastics material injected into the mould. Althoughthe connecting sheet appears in these drawings to be flush, in realityand bearing in mind the fact that the injection process makes itpossible to feed the material from either side of the sheet, for exampleby additionally injecting plastics material from the male die, to bemore precise the sheet is incorporated in the support 8.

After removal from the mould, a continuous cutout 14 was producedforming a flat indent in the part, for example with the help of a laser.This cutout 14 is produced from the non-visible face 1 b and extendstowards the visible face 1 a, though without opening out into saidvisible face 1 a. The cutout 14 passes through the sheet 6 and part ofthe thickness of the support 8, thereby constituting a mechanicalweakening of this support. This leaves a thickness of less than 0.3millimetre between the floor of said flat indent 14 and the visibleface.

The cutout 14 extends between two extremities 14 a, 14 b disposed facingthe loop 2 of the connecting sheet 6. Overall this cutout 14 is U-shapedand defines an embrittled portion in which the sheet is absent.

Between the extremities 14 a and 14 b, an articulating portion 20 isdefined which extends along an articulation axis 30. The articulatingportion 20 does not present a cutout in the connecting sheet 6. It couldbe mechanically weakening, though this is not the case in FIGS. 3 and 4.This articulating portion is overlapped by the connecting sheet 6 whichextends continuously on either side of the articulation axis 30.

The articulating portion 20 and the weakened portion 14 define theperiphery of a special opening zone 15 which forms a door for an airbagmodule 28 disposed on the side of the non-visible face 1 b.

For ease of comprehension the articulating portion 20 has beensymbolised by crosses, and the thickness of the sheet and of the supporthas been increased with respect to their other dimensions.

It appears in FIG. 4 that the door 15 and in particular its periphery iswholly and strictly enclosed within the zone defined by the externalcontour of the connecting sheet 6. Accordingly, the connecting sheet 6is present over the whole of the door and also to either side of itsentire periphery. This makes it possible to give the facia panel 1better resistance to fracture over the door and over the part thereofexternal to the door. The part 6 a of the sheet present over the door isjoined to the part that is outside the door—known as the fringe part 6b—via the loop 2 of the connecting sheet and hence via the articulatingportion 20.

So that the door is entirely enclosed within the zone defined by theexternal contour of the connecting sheet, once this sheet has beenintroduced into the mould it presents a length and breadth greater thanthose of the door 15. Advantageously, the sheet presents a length L—i.e.perpendicular to the articulation axis—and a breadth 1—i.e. parallel tothe articulation axis—substantially equivalent to 50 centimetres with amargin of the order of 25%, bearing in mind that the door has generallya length overall of 10 to 15 centimetres and a breadth of 25 to 30centimetres. Accordingly, the sheet and to be more precise its fringeportion opens out at least 5 centimetres beyond the door, onto theremainder of the facia panel. This makes it possible to obtain a faciapanel of satisfactory mechanical strength, bearing in mind thatfracturing of the embrittled portion is generally obtained in respect ofa pressure applied to the whole of the door of between 10⁵ and 10⁷ Pa(preferably close to 2.10⁵ Pa).

In FIG. 5, under the force of airbag deployment spreading out over thedoor 15, the facia panel 1 and to be more precise the support 8,ruptures in the weakened portion 14, thereby causing the door 15 topivot about the articulation axis 30 and to produce a passageway 17through the facia panel 1. This pivoting of the door about thearticulation axis 30 is made possible by the excess length of theconnecting sheet 6 formed by the loop 2—which defines a redundantsection—which furthermore makes it possible to keep the door 15 with therest of the facia panel 1. This is because the plastics support 8 is indanger of fracturing in the articulating portion 20 under the strain dueto this pivoting action.

FIG. 6 presents an alternative embodiment of the facia panel 1. Thispanel is distinguished from that shown in FIGS. 1 to 5 by the fact thatit is mechanically weakened in the articulating portion 20 as the resultof a groove 34 obtained when the part is being moulded and due to thefact that it is referred to a body 35 to which it is attached by weldingalong a peripheral line 36. The mechanically weakened area 20 is formedby a constriction produced on the visible face 1 a. This constrictioncould be produced on the non-visible face 1 b. Its function is to helpthe door to articulate and to make it possible to omit the redundantsection (excess length of sheet) facing the articulating portion, takingaccount of the reduced thickness of plastic.

Furthermore, the sheet 6 comprises a main part 31 which extends for theentire length—but not necessarily for the entire breadth—of thenon-visible face 1 b of the part 1. In particular, beyond thearticulating portion 20, the sheet extends, in a direction perpendicularto the articulation axis 30, as far as the edge 8 a of the part. It evengoes on beyond the support 8 via a connecting tongue 32 joined to therest of the sheet. The main part 31 is fixed to the support 8, in otherwords joined intimately to this support by virtue of the mouldingoperation. The connecting tongue 32 is not in contact with the support8, with the result that it is connected thereto but not fixed onto it.

The sheet 6 and more specifically the connecting tongue is connected tothe body 35 via a fixing screw 38. It therefore creates a secondaryconnecting means between the facia panel body 35 and the part 1.Accordingly, if the force created by the deployment of the airbag wereto cause the weld line 36 to fracture, in spite of this, the part 1would still be retained on the facia panel 35 by the tongue 32.

The part 1 is obtained by arranging the sheet in the mould cavity andleaving part of said sheet sticking out so as to define the tongue, insuch a way that the latter is not covered by plastic.

In FIG. 7, the part incorporates a cutout 39 which defines theembrittled portion extending within the thickness of the part, from thenon-visible face 1 b to the visible face 1 a. Unlike in the precedingfigures, this cutout 39 does not follow the line 27 normal to thenon-visible face 1 b (to the support 8). The direction of the cutout isinclined by an angle α to the outside of the door 15, relative to thisnormal line 27. Here the angle α is approximately 45 degrees;advantageously it will be between 30 degrees and 60 degrees.

Accordingly, if a force F is applied to the door 15 from the side of thevisible face 1 a, the inclination of the cutout will mean that this door15 will have no option but to pivot very slightly about the articulationaxis 30.

In FIG. 8, a retaining element 42, here a U-shaped bracket, is arrangedso as to rest against the non-visible face 1 b of the facia panel. It isfixed to the facia panel 1 via fixing means 45 such as screws to theoutside of the door 15. This bracket 42 overlaps the cutout 14, suchthat if a force F is exerted on the visible face 1 aof the door 15, thelatter will come up against the bracket 42 and cannot be retracted. Thedoor 15 is thus able to open in only one direction.

The airbag module 28 is fixed to a crossbeam 40 adapted in particular tohelp keep the facia panel 1 in place, but it is not connected to thebracket, which makes it easier to install the various elements on thevehicle. Furthermore the bracket 42 possesses a widened portion 44 whichincreases in size in the direction of the facia panel. This widenedportion disposed opposite where the airbag module 28 will be inflated isused to guide the airbag when it is deployed.

FIG. 9 depicts a connecting sheet 46 which presents a latticeworkstructure. This structure, which may in particular be obtained by theuse of a woven or knitted material, produces interstices 46 a adapted tobe filled with the plastics material and thus allowing better adhesionwith that material. This sheet is not brittle, but flexible within thetemperature range for which the vehicle is designed.

FIG. 10 shows a part 51 having a connecting sheet 56 which presentscells 56 a filled with the plastics material of the support 8. Thesecells improve the joint between the connecting sheet 56 and the support8.

Furthermore, on its visible face 51 a the part incorporates a complex 53comprising a covering sheet 52 and a foam layer 54. Accordingly, on itsvisible face 51 a it presents a high-quality appearance and a flexiblefeel and on its non-visible face 51 b it has the flexible connectingsheet 56.

This part is obtained by arranging the complex 53 in the mould, so thatit rests against the female die 12 a.

If the covering sheet is a self-sealing material, such as polyvinylchloride, it will be possible to make a quasi-through-cutout, or even athrough-cutout.

In the various figures, for ease of comprehension the thicknesses of theconnecting sheet 6, of the support 8 and of the complex 53 have beenproportionally increased with respect to the overall dimensions of thefacia panel. In reality, such a facia panel will present a width ofapproximately 1.5 metres, a length (height) of 50 centimetres and athickness of between 2 and 50 millimetres, around 10%. The connectingsheet advantageously has a thickness of between 0.1 millimetre and 3millimetres. In the case of a plastics injection-moulded unilayer faciapanel, the plastics material will advantageously have a thickness ofbetween 1 and 6 millimetres. In the case of a multilayer facia panel,the covering sheet will advantageously have a thickness of between 0.2millimetre and 6 millimetres, the thickness of the foam layer or layerswill advantageously be between 2 and 50 millimetres and the thickness ofthe support will be between 1 and 6 millimetres.

It will be readily understood that the invention is by no meansrestricted to the embodiments illustrated. Thus in FIG. 6, the sheet 6need not have a tongue 32 coming out of the support 8—notably byslightly modifying the end of the support 8, in particular making itU-shaped—the main thing being to connect the sheet 6 to the body 35. Thefixing screw 38 would then pass through the body 35, the support 8 andthe sheet 6.

Upon its being introduced into the mould the connecting sheet couldalready incorporate a cutout defining a flat indent characterised by theabsence of the connecting sheet at the place where it is desired toproduce the embrittled portion in the finished part.

Likewise it would be possible to provide for two U-shaped cutouts to bemade, one on top of the other and running in opposite directions, withthe result that overall the flat indent would present the shape of an H:two articulation axes being provided, one at the foot of the H, and theother at the head of the H.

The cutout could be produced as a line of dots, constituted by a seriesof holes set very close to one another, advantageously with a diameterof between 0.05 millimetre and 0.5 millimetre and spaced between 0 to 2millimetres apart from one another—preferably between 0.5 and 0.7millimetre in the case of a polypropylene support.

The cutout could likewise be triangular in section.

What is claimed is:
 1. A method for producing a passageway for anairbag, comprising the steps of: a) providing a mold comprising a femaledie, a male die, and a moveable insert movable between a retractedposition and an advanced position, the movable insert is retracted intoa cavity on the male die, wherein a slot is produced between the movableinsert and the male die when the movable insert is in the retractedposition, and the movable insert extends outwardly from the male diewhen in the advanced position; b) introducing a connecting sheet into amold cavity of the mold with the movable insert at the advancedposition; c) moving the movable insert to the retracted position suchthat a folded section of the connecting sheet is trapped in the slot; e)introducing plastic material into the mold cavity having the connectingsheet therein to form a part comprising a plastic support element havinga reduced thickness in comparison to its other dimensions and theconnecting sheet extending substantially along and over a surface of thesupport element, wherein the plastic material contacts each face of theconnecting sheet in order to encompass the connecting sheet in thesupport element; f) forming a special opening zone having a peripherywithin the part, the periphery of the special opening zone is defined byan embrittled portion that has been mechanically weakened between twoextremities of the special opening zone and an articulating portionwhich defines between the two extremities an articulation axisoverlapped by the connection sheet so that the connecting sheet ispresent on either side of the embrittled portion, along at least a majorpart of the embrittled portion, and over at least a greater part of thespecial opening zone.
 2. The method according to claim 1, wherein, instep f), in at least part of the embrittled portion, simultaneously acutout is made in the connecting sheet and the support element ismechanically weakened by excising part of the thickness thereof.
 3. Themethod according to claim 1, wherein, in step f), the embrittled portionis enclosed within the connecting sheet.
 4. The method according toclaim 1, wherein, in step e), the connecting sheet substantially coversthe-part in a direction perpendicular to the articulation axis, the partis attached to a body by fixing, and the connecting sheet is affixed tothe body.
 5. The method according to claim 3, wherein, in step e), atongue of said connecting sheet protrudes from the mold cavity andconnects to a body.
 6. The method according to claim 1, wherein saidslot has a thickness twice the size of said connecting sheet.
 7. Themethod according to claim 1, wherein said molding material is introducedinto said mold cavity after said folded section of said connecting sheetis retained in said slot.